Phototherapy applied to humans seems to be an effective treatment, in particular with regard to Seasonal Affective Disorder which is a form of depression, the main characteristic of which is that it occurs during the same period each year, usually at the start of autumn or winter and lasting through to spring.
Applied to an individual, phototherapy (sometimes known as luminotherapy) may consist in exposure to bright light (between 2500 and 10000 lux on the cornea) for a certain period of time and in a controlled environment. The information relating to this light, which is detected by the eyes, is then transmitted via the optical nerve to the suprachiasmatic nucleus of the hypothalamus which controls the neurological and endocrinal circadian rhythms, with an effect on the concentration, mood, and physical and psychological performance of the individual.
Melatonin is one of the favoured markers of the effects of light on the suprachiasmatic nucleus and the epiphysis.
Important photometric parameters for effective treatment are therefore                the luminous flux proportional to the amount of photons received by the human eye per unit time, expressed either in lumens or in watts,        the incident light, defined as the luminous flux per unit surface area and expressed either in lux or in watt/m2,        the amount of light, defined by multiplying the light by the duration of exposure and expressed in lux.s.        
Phototherapy devices are primarily known in two forms, namely:                non-portable lighting units which require the individual being treated to remain in one place during each exposure session and which, if the individual wishes for example to read during this time, exhibit a considerable loss of effectiveness due to the fact that the individual lowers his eyelids which then form a screen against the treatment light, and        portable lighting units which are fixed to the head in the manner of a helmet or headband or in the form of spectacles, which either supply light to the eyes directly from above and suffer from the same problem concerning the eyelids as forms an obstacle to the aforementioned light when the individual wishes in particular to read, or do not allow any activity since they inundate the entire field of vision with light.        